Strap feed track with fluid-actuated strap end positioning means

ABSTRACT

A binder strap track includes a stationary section and a movable section movable therealong for varying the track length, each section comprising a backing wall having a strap guide surface and a retainer cooperating therewith to define a strap path. A discontinuity in the strap guide surface is formed at the junction of stationary and movable sections thereof. The stationary section of the backing wall has an elongated slot therein adjacent to the discontinuity. Disposed in the slot is a fluid conduit, substantially rectangular in transverse crosssection, with the outer wall thereof perforated and having an outer surface thereon substantially coplanar with the adjacent portions of the stationary section of the strap guide surface. Compressed air is introduced into the conduit and produces jets of air through the perforation for urging the associated strap away from the strap guide surface and the discontinuity therein and toward the strap retainer.

United States Patent [191 Johnson [451 Aug. 27, 1974 STRAP FEED TRACK WITH FLUID-ACTUATED STRAP END POSITIONING MEANS [75] Inventor: Robert A. Johnson, Flossmoor, Ill. [73] Assignee: Interlake, Inc., Chicago, Ill.

[22] Filed: Dec. 26, 1972 [2]] Appl. No; 318,634

Primary Examiner-Billy Wilhite Attorney, Agent, or FirmPrangley, Dithmar, Vogel, Sandler & Stotland [57] ABSTRACT A binder strap track includes a stationary section and a movable section movable therealong for varying the track length, each section comprising a backing wall having a strap guide surface and a retainer cooperating therewith to define a strap path. A discontinuity in the strap guide surface is formed at the junction of stationary and movable sections thereof. The stationary section of the backing wall has an elongated slot therein adjacent to the discontinuity. Disposed in the slot is a fluid conduit, substantially rectangular in transverse cross-section, with the outer wall thereof perforated and having an outer surface thereon substantially coplanar with the adjacent portions of the stationary section of the strap guide surface. Compressed air is introduced into the conduit and produces jets of air through the perforation for urging the associated strap away from the strap guide surface and the discontinuity therein and toward the strap retainer.

l 5 Clains, 6 Drawing Figures PATENIEUAUGZHHM SKUZNZ STRAP FEED TRACK WITH FLUID-ACTUATED STRAP END POSITIONING MEANS This invention relates to strapping machines for securing a binder strap about objects to be bound and, in particular, to a track for guiding the binder strap about the object to be bound.

It is a general object of this invention to provide a binder strap track provided with a strap guide surface having a discontinuity therein, and means for urging the leading end of the strap away from the strap guide surface in the area of the discontinuity to prevent the strap from snagging on this discontinuity as it traverses the strap path. V

More particularly, this invention relates to a strap track of the type described, wherein the discontinuity occurs at the junction between movable and stationary sections of the strap track.

It is an important object of the present invention to provide a binder strap track for guiding a binder strap around an object to be bound located at a strapping station, the track comprising a strap guide surface extending substantially about the strapping station, a strap retainer mounted adjacent to the strap guide surface for cooperation therewith to define a path for the associated strap about the strapping station, the associated strap being normally biased toward engagement with the strap guide surface .as the strap traverses the path, the strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and means urging the associated strap away from the guide surface and toward the retainer in the region of the discontinuity for preventing the associated strap from engaging the discontinuity as the strap traverses the path.

In connection with the foregoing object, it is another object of this invention to provide a binder strap track of the type set forth, wherein the urging means comprises means for directing a stream of fluid against the associated strap in the region of the discontinuity for urging the strap away from the guide surface and toward the retainer.

In connection with the foregoing object, still another object of this invention is to provide a binder strap track of the type set forth, which includes a backing wall having the strap guide surface thereon, and a fluid conduit formed in the backing wall and adapted to be coupled to an associated source of pressurized fluid, the strap guide surface having an opening therein adjacent to the discontinuity communicating with the conduit for allowing passage therethrough of a stream of compressed fluidfor urging the associated strap away from the guide surface and toward the retainer.

In connection with the foregoing object, yet another object of this invention is to provide a binder strap track of the type set forth, which includes a stationary section and a movable section, the strap guide surface on the stationary section cooperating with that of the movable section to form the discontinuity therebetween, the fluid conduit being carried by the stationary section of the backing wall.

Further features of the invention pertain to the particular arrangement of the parts-of the binder strap track whereby the above-outlined and additional operating features are attained.

The invention, both as to its organizationand method of operation, togetherwith further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a front elevational view of a binder strap track constructed in accordance with and embodying the features of the present invention, and illustrating the positions between which the movable portion of the track assembly may move;

FIG. 2 is an enlarged fragmentary front elevational view of the left-hand portion of the track, as viewed in FIG. 1, and illustrating the pneumatic strap positioning assembly;

FIG. 3 is a further enlarged fragmentary side elevational view in partial section of the portion of the track illustrated in FIG. 2;

FIG. 4 is a fragmentary end elevational view of the backing wall and fluid conduit of the portion of the track shown in FIG. 2, as viewed from the right-hand side thereof;

FIG. 5 is an enlarged view in horizontal section of the backing wall and fluid conduit taken along the line 5-5 in FIG. 4; and

FIG. 6 is an enlarged view in horizontal section of the strap track taken along the line 6-6 in FIG. 2, and illustrating the different positions of the strap retainer.

This invention is an improvement of the Adjustable Platen Track disclosed in the US. Pat. No. 3,613,557, issued to Bestor P. Coleman on Oct. 19, 1971, and as signed to the assignee of the present invention. Referring to FIG. 1 of the drawings, there is illustrated a strapping machine, generally designated by the numeral 100, including a base frame 102 which is made up of a pair of side frame members 103 interconnected by bottom frame members 104 to form a stable base for the strapping machine 100. Mounted on the base frame 102 and extending upwardly therefrom are a pair of spaced-apart bearing members 106 having journaled' therein the opposite ends of a conveyor roll 105. Preferably, a plurality of the conveyor rolls I05 areprovided and cooperate to define a substantially horizontal conveyorplatform for supporting thereon an object 107 to be strapped.

' Mounted upon the base frame 102 and extending about the location where the object 107 is positioned, on the conveyor rolls is a generally rectangular binder strap track, generally designated by the numeral 110. The track 110 comprises astationary section including a bottom horizontal flight 111 and two vertically extending flights 112 and 113 and interconnected by corner sections 130, and a movable section in the form of a movable platen assembly, generally designated by the numeral 140, extending between the vertical flights 112 and 113 above andsubstantially parallel to the bottom flight 111. l

As will be described in greater detail hereinafter, the binder strap track 110 defines a path 135 for guiding an associated strap web.1l5 about the object 107 to be strapped. More particularly, the track 110 includes a plurality of substantially identically constructed backing rails 120, 121, and 127, each being formed of solid bar stock substantially rectangular in transverse cross section. The backing .wall is mounted'on the base frame 102. and extends horizontally therealongsubstantially parallel to the conveyor rolls 105. The backing rails lZI and 127 are respectively spaced a slight distance outwardly of the right-hand and left-hand ends of the bottom backing rail 120, as viewed in FIG. 1, the backing rail 121 being secured to the base frame 102 by an angle bracket 122 and extending substantially vertically upwardly therefrom, and the backing rail 127 being coupled to the base frame 102 by an angle bracket 124 and extending upwardly therefrom substantially parallel to the backing rail 121. The backing rail 127 terminates at an upper end substantially in horizontal alignment with the upper end of the backing rail 121. Each of the backing rails 120, 121 and 127 is arranged with one of the narrow side surfaces 128 thereof arranged inwardly of the track 110 to define a backing wall for the associated strap, as will be described more fully hereinafter.

Respectively connecting the opposite ends of the bottom backing rail 120 to the adjacent portions of the backing rails 121 and 127 are two corner sections, each generally designated by the numeral 130. The corner sections 130 are identically constructed and are preferably roller sections, the detailed construction of the corner roll sections 130 being disclosed in the copending US. application Ser. No. 64,434 of Bestor P. Coleman filed Aug. 17, 1970, entitled STRAP TRACK FOR STRAPPING MACHINE, and assigned to the assignee of the present invention, now US. Pat. No. 3,768,396. Each of the corner roll sections 130 includes a pair of side plates 131 extending between the adjacent ends of the backing rails 120, 121 and 123 and respectively coupled to the front and rear surfaces thereof. More particularly, each of the side plates 131 is connected adjacent to the lower end thereof to a mounting plate 134 which is in turn coupled to the adjacent end of the bottom backing rail 120, the upper ends of the side plates 131 being respectively coupled to the backing rails 12] and 127. Mounted for rotational movement between the side plates 131 are a plurality of interleaved roll groups (not shown), each preferably including several rolls arranged coaxially transversely of the side plates 131 with the circumferential surfaces thereof cooperating to define an arcuate backing surface which is substantially flush with the backing walls 128 on the adjacent backing rails. Respectively connected to the outer surfaces of the side plates 131 for movement between retaining positionsand releasing positions is a pair of retainers 133, the retainers 133 in the retaining positions thereof cooperating with the roller groups to define the adjacent corner portions of the path 135 for the associated strap 115.

Extending between the backing rails 121 and 127 for movement longitudinally therealong is the movable platen assembly 140, which includes a strapping head 145 provided with a feed wheel 149 therein for feeding the associated binder strap 115 from a supply thereof into the'path 135 defined by the track 110. The strapping head 145 is preferably disposed substantially midway between the backing rails 12] and 127 and has secured to the opposite ends thereof two upper backing rail sections 141 and 142 respectively extending toward the backing rails 121 and 127 in alignment with each other and substantially parallel to the bottom backing rail 120. Each of the upper backing rail sections 141 and 142 is of the same cross-sectional construction as the backing rails 120, 121 and 127. Each of the top backing rail sections 141 and 142 is provided at the outer end thereof with a pair of end plates 143 respectively secured to the front and rear surfaces thereof and extending outwardly therefrom substantially perpendicular to the adjacent vertical backing rail 121 or 127. Secured to each of the end plates 143 by suitable means is another of the comer roll sections 130, constructed as described above and respectively defining upper corner portions of the strap path 135 for coupling the movable platen assembly 140 to the vertically extending track flights 112 and 113.

The movable platen assembly 140 is preferably supported by suitable drive apparatus (not shown) for effecting movement of the movable platen assembly 140 upwardly and downwardly longitudinally of the vertically extending backing rails 121 and 127. In order to facilitate and guide this vertical movement of the movable platen assembly 140, each of the end plates 143 is provided adjacent to the outer end thereof with a guide wheel 148 having the outer circumferential surface thereof disposed in rolling engagement with the backing wall 128 of the adjacent backing rails 121 or 127.

The lower end of each of the upper corner roll sections 130 is necessarily spaced inwardly a slight distance from the adjacent backing wall 128 to accommodate free passage of the movable platen assembly 140 therealong. In practice, the strapping head 145 may be so arranged as to feed the strap web 115 in either direction around the track 110. However, in the preferred embodiment, the strapping head 145 has been illustrated in a configuration for feeding the strap web in a clockwise direction around the track as viewed in F 1G. 1. The strap web will ordinarily be fed to the strapping head 145 from a suitable supply coil in such a manner that the normal curvature of the strap web 115 imparted by the coil, will tend to urge the leading end of the strap web 115 outwardly against the backing wall 128 of the track 110. Accordingly, as is explained in the aforementioned copending application Ser. No. 64,434, the leading end of the strap web 115 will tend to follow the backing wall 128 and the roller groups of the corner roll sections as it travels around the track 110, whereby there will be no possibility of the leading end of the strap web 115 snagging or hanging up in the track 110 until it reaches the upper left-hand corner roll section 130.

Since this corner roll section 130 is spaced a slight distance inwardly of the backing wall 128, the leading end of the strap web 115 would nonnally tend to follow the backing wall 128 and snag 0n the discontinuity in the backing wall formed by the lower end of this corner roll section 130, thereby jamming the strap web 115 in thetrack 110.

More particularly, referring to FIG. 2 of the drawings, an angle bracket 146 is provided on the upper lefthand comer roll section 130, the angle bracket 146 having a relatively short horizontally extending leg 144 secured by suitable means to the adjacent end plates 143, and a downwardly extending relatively long leg 147 disposed along the adjacent backing wall 128 of the backing rail 127 substantially parallel thereto. The lower end of the downwardly extending leg is tapered as at 147a to facilitate the passage of the leading end of the strap web 115 from the vertical flight 113 of the strap track 110 to the upper left-hand comer roll section 130, but nevertheless, this end 147a of the leg 147 creates an unavoidable discontinuity or obstruction in the strap guide surface 128 of the vertical flight 113 which tends to snag the leading end of the strap web 1 and cause buckling in the strap web as it traverses the path 135.

In order to prevent such snagging, there is provided a strap end positioning apparatus, generally designated by the numeral 150, and illustrated in FIGS. 2 through 6 of the drawings. Formed centrally of the strap guide surface 128 of the backing wall 127 adjacent to the upper end thereof is an elongated slot or groove 151 substantially rectangular in transverse cross section, and having snugly received therein a hollow tubular fluid conduit 153 which is also substantially rectangular in transverse cross section. The outer wall 1560f the conduit 153 is provided with a flat planar outer surface 158 which is disposed in use substantially coplanar with the adjacent surrounding portions. of the strap guide surface 128 of the backing wall 127 for providing a substantially continuous strap-guide surface for the strap web 115 in the area of the conduit 153. The outer wall 156 of the conduit 153 is also provided with a plurality of apertures or openings 155 therethrough, the openings 155 being arranged in two vertical rows of spaced-apart openings, with the openings in one row being staggered vertically with respect to the openings in the other row, as is best illustrated in FIG. 4. The conduit 153 is coupled at the upper end thereof to a supply conduit 152 by means of a fitting 154, the supply conduit 152 in turn being preferably coupled to an associated source (not shown) of compressed air.

In use, compressed air is introduced into the conduit 153 from the associated source and passes downwardly therethrough in the direction indicated by the arrow in FIG. 3, the compressed air then emerging through the openings 155 as a plurality of high velocity streams or jets of air directed as indicated by the arrows in F IGS. 2 and 5. As the strap web 115 passes over the openings 155, the jets of air emanating therefrom bear against the strap web 115 actively applying to it a force which urges it outwardly away from the strap guide surface 128 and toward the retaining flanges 185 of the retainers 180, as indicated in FIGS. 2 and 6, thereby preventing the leading end of the strap web 115 or any other portion thereof from engaging the lower end 147a of the angle bracket leg 147. As soon as the strap web 115 has passed by the openings 155 and up into the upper left-hand corner roll section 130, the natural camber of the strap will again urge the leading end thereof back toward engagement with the strap guide surface 128.

Mounted on each of the backing rails 120, 121, 127, 141 and 142 and cooperating therewith to define the strap path 135 and retain the strap 115 therein are a plurality of pairs of strap retainers, including generally U-shaped constant-width retainers 160, reducing retainers 160a and generally L-shaped retainers 180. The backing rails 120, 121 and 141 are provided solely with the generally U-shaped retainers 160, each .of the retainers 160 being identicallyv constructed and the detailed construction thereof being disclosed in the aforementioned U.S. Pat. No. 3,6l3,557.

Referring now again to FIGS. 4 and 5 of the drawings, the reducing retainers 160a are substantially similar in construction to the retainers 160. The construction of the reducing retainers 160a also being disclosed in the aforementioned US. Pat. No. 3,6l3,557. One pair of the reducing sections 160a is disposed immediately below the lowest point of travel of the movable platen assembly 140 for more positively and accurately positioning the leading end of the strap web 115 into the left-hand corner roll section of the movable platen assembly 140. Similarly, another pair of reducing retainers 160a is disposed adjacent to the strapping head in the exit end of the track 110 tovprovide more positive and accurate positioning of the leading end of the strap web 115 in the strapping head 145. All of the other retainers carried by the top backing rail section 142, and all of the retainers disposed below the reducing retainer a in the vertical track flight 113 of the U-shaped retainers 160.

All of the retainers in the vertical track flight 113 above the reducing retainers 160a are the standard L- shaped retainers 180. The retainers 180 are identically constructed, whereby only one of the retainers 180 will be described in detail. Referring in particular to FIG. 6 of the drawings, each of the retainers 180 includes a flat side plate 182 extending longitudinally of the associated backing rail, the side plate 182 being provided with an inwardly extending retaining flange 185 integral with the upper end thereof and disposed substantially normal thereto. The retaining flange 185 extends the entire length of the side plate 182 and is provided at the entry end thereof with an out-turned generally triangular lip portion 184. Integral with the lower end of the side plate 182 and extending outwardly therefrom at an obtuse angle thereto is a skirt flange 186. The side plate 182 is provided with two spring openings 187 and 188 therein, respectively identical in construction, position and function to like spring openings in the retainers-160. Accordingly, tension springs 181 are coupled between each pair of retainers 180 for urging them toward each other in the same manner as was described with respect to the retainers 160 in US. Pat. No. 3,613,557. V

In addition, each pair of retainers 180 is provided with support pin openings 'therethrough identical in construction, position and function to like support pin openings in the retainers 160. Accordingly, support pins are received throughthe corresponding openings in each pair of retainers for supporting the retainers 180 for movement between retaining and releasing positions thereof, respectively illustrated in solid line and broken line in FIG. 6. As indicated in FIG. 6, when the retainers 180 are in the retaining positions thereof, the retaining flanges are spaced a short distance from the associated backing wall 128 and are disposed substantially parallel thereto for de fining therewith the adjacent portion of the strap path 135. In this position, the inner ends of the retaining flanges 185 are spaced apart a slight distance substantially less than the width of the strap 115 to'confine to strap 115 to the path 135, the separation between the flanges 185 and the backing wall 128 being substantially greater than the thickness of the strap '1 15 to accommodate ready passage thereof along the path.

It will be-noted that the side plates 182 in the retaining positionsthereof are spaced apart a distance substantially equal to the width'of the backing wall 128 whereby the portion of the path defined thereby has a width-only slightly greater than the width of the associated strap. When the retainers 180 are in their releasing positions, the inner edges of the retaining flanges 185 are respectively disposed outwardly of the adjacent side edges of the backing wall 128 to accommodate easy removal of the associated strap 115 from the track. 110. The retainer'pairs 160, 1600 and 180 are all arranged in substantially end-to-end relation along each straight flight of the track 110, so as to cooperate with the corner roll sections 130 to define a continuous path 135 around the object strapping location.

If desired, the side plates 182 of the retainers 180 may be elongated so as to enlarge the spacing between the strap guide surface 128 and the retainer flange 185 for widening the strap path 135 in the area of the conduit 153, thereby to provide even greater clearance of the angle bracket leg 147 by the strap web 115 to insure that there will be no engagement of the angle bracket leg end 147a by the strap web 115.

Referring to FIGS. 1 and 2 of the drawings, it will be noted that platen follower assemblies, generally designated by the numeral 190, have been provided, the follower assemblies 190 being coupled to the opposite ends of the movable platen assembly 140 by appropriate means (not shown) and movable therewith. The follower assemblies 190 are identically constructed and the same reference numerals have been applied to like parts of each. Each assembly 190 includes a vertically extending arm 191 disposed outwardly of the backing rail 127 substantially parallel thereto and carrying a clevis block 192 at the upper end thereof. Mounted for rotation about a shaft journaled in the clevis 192 is a guide roll 193, so dimensioned and arranged that the circumferential surface thereof is disposed in rolling engagement with the outer surface of the adjacent backing rail 121 or 127 for guiding the movement of the follower assembly 190 therealong.

Also carried by the arm 190 at spaced-apart points therealong are several pairs of retainer opening rolls 195, respectively disposed adjacent to the front and rear sides of the adjacent retainers for rolling engagement with the skirt flanges 166 or 186 thereof. The topmost pair of retainer opening rolls 195 is preferably disposed above the guide roll 148 on the movable platen assembly 140, while the bottommost pair of retainer opening rolls 195 is disposed adjacent to the lower ends of the corner roll sections 130 on the movable platen assembly 140. Thus, it will be readily appreciated that as the movable platen assembly moves upwardly and downwardly along the vertical backing rails 121 and 127, the retainer opening rolls 195 will engage the skirt flanges 166 and 186 of the adjacent retainers 160 and 180 for urging the retainers 160 and 180 to the releasing positions thereof, thereby accommodating passage of the angle bracket leg 147 and the lower ends of the upper guide roll sections 130 and the guide rolls 148 along the associated backing rails between the open retaining flanges 165 and 185 of the retainers 160 and 180. As the movable platen assembly 140 moves upwardly above the location of a given pair of retainers 185, the retainer opening rolls move out of engagement therewith to permit the retainers 180 to be returned to the retaining position thereof by the tension springs 161.

ln operation, when it is desired to apply a binder strap about an object 107, the object 107 is first placed in position on the conveyor rolls 105 within the track 110, the movable platen assembly having first been adjusted to the proper height to accommodate the object 107 within the track 110. The leading end of a length of strap web 115 is then fed by the strapping head 145 into the path 135 defined by the track 110 and in a clockwise direction therearound. When the leading end of the strap web 115 passes over the apertures 155 of the conduit 153, the jets of compressed air urge the strap web outwardly against the retainer flanges 185 away from the lower end 147a of the angle bracket flange 147 to prevent engagement thereof by the strap web 115. The strap web 115 then passes upwardly directly into the comer roll section at the left-hand end of the movable platen assembly 140.

The leading end of the strap web 115 is then fed back into the strapping head and into overlapping relationship with the supply portion of the strap web 115, in a well-known manner.

At this point, the strap web 1 15 is pulled by the strapping head 145 into a tensioned condition about the object 107, the corresponding contraction of the loop of the strap about the object 107 causing the strap web 115 to engage the retaining flanges 165, a and of the retainers 160, 160a and 180, respectively, for moving the retainers 160, 160a and 180 into the releasing positions thereof against the urging of the bias springs and releasing the strap web 115 from the path. After the strap has been tensioned about the object 107 it is sealed thereabout and severed from the supply portion of the strap 115, whereupon the strapped object 107 may be removed from the strapping machine 100, all in a well-known manner.

If it is desired to utilize the strapping machine 100 to apply a strap about a different size object 107, an appropriate upward or downward adjustment in the position of the movable platen assembly 140 is made, after which the above-described strapping operation is repeated. The upward or downward movement of the movable platen assembly 140 is accompanied by corresponding movement of the follower assemblies to move the adjacent retainers to their releasing positions, thereby accommodating passage of the adjacent end of the movable platen assembly 140 therebetween.

From the foregoing, it will be seen that there has been provided an improved binder strap track provided with a strap guide surface having a discontinuity therein, and including means for urging the strap web away from the strap guide surface and the discontinuity as the strap web traverses the track.

More particularly, there has been provided an improved binder strap track of the character described, wherein the means for urging the strap away from the discontinuity comprises means for directing streams of compressed fluid against the strap for urging it away from the discontinuity.

There has also been provided a binder strap track comprising a stationary section and a movable section movable with respect to the stationary section for varying the length of the strap path, the discontinuity in the strap guide surface being formed at the junction between the stationary and movable sections and the means for urging the strap away from the discontinuity being carried by the stationary section.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide surface extending substantially about the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping station, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and means actively applying to the associated strap a force urging it away from said guide surface and toward said retainer only in the region of said path immediately upstream of said discontinuity for preventing the associated strap from engaging said discontinuity as the strap traverses said path.

2. The binder strap track set forth in claim 1, wherein said path is substantially rectangular in shape.

3. The binder strap track set forth in claim 1, wherein said strap retainer is movable between a retaining position for cooperation with said strap guide surface to define said path and a releasing accommodating removal of the associated strap from said path.

4. The binder strap track set forth in claim 1, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperation to form said discontinuity at the junction therebetween.

5. The binder strap track set forth in claim 1, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junction therebetween, said urging means being carried by said stationary section of said strap guide surface.

6. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide surface extending substantially about the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping section, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and strappositioning means for directing a stream of fluid against the associated strap only in the region of said path immediately upstream of said discontinuity to urge the strap away from said guide surface and toward said retainer thereby to prevent the strap from engaging said discontinuity as the strap traverses said path.

7. The binder strap track set forth in claim 6, wherein said fluid is compressed air. I

8. The binder strap track set forth in claim 6, wherein said strap positioning means directs a plurality of jets of fluid against the associated strap for urging the strap away from said guide surface.

9. The binder strap track set forth in claim 6, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junctions therebetween.

10. The binder strap track set forth in claim 6, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junction therebetween, said strap positioning means being carried by said stationary section of said strap guide surface.

11. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a backing wall having a strap guide surface thereon extending substantially about'the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping station, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and a fluid conduit formed in said backing wall and adapted to be coupled to an associated source of pressurized fluid, said fluid conduit having an opening therein communicating with the strap path only immediately upstream of said discontinuity and accommodating passage therethrough of a stream of compressed fluid for urging the associated strap away from said guide surface and toward said retainer to prevent the associated strap from engaging said discontinuity as the strap traverses said path.

12. The binder strap track set forth in claim 11, wherein said path is substantially rectangular in shape, said discontinuity being disposed adjacent to one of the comers of said path.

13. The binder strap track set forth in claim 11, wherein said conduit has a plurality of openings therein adjacent to said discontinuity communicating with said path and accommodating passage therethrough of a plurality of streams of compressed fluid.

14. The binder strap track set forth in claim 11, wherein said strap guide surface being substantially planar and having an elongated slot therein adjacent to said discontinuity, said fluid conduit being received in said slot with a portion of the wall of said conduit having the outer surface thereof disposed substantially coplanar with the adjacent portion of said strap guide sur- 1 1 face, said opening being formed in said outer surface of said fluid conduit.

15. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide defining a path for the associated strap extending substantially about the strapping station said strap guide including a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, each of said sections including a backing wall having a strap guide surface thereon and a strap retainer cooperating with said strap. guide surface to define the adjacent section of said path therebetween, the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said stationary section strap guide surface and said movable section strap guide surface cooperating to form a discontinuity therebetween which impedes the passage of the associated strap therealong, said stationary section backing wall having an elongated slot in said strap guide surface thereof substantially rectangular in transverse crosssection, and a fluid conduit substantially rectangular in cross-section disposed in said slot and adapted to be coupled to an associated source of pressurized fluid, said fluid conduit having an outer wall provided with a plurality of openings therethrough and having the outer surface thereof disposed substantially coplanar with the adjacent portion of the stationary section strap guide surface, said openings accommodating passage therethrough of streams of compressed fluid for urging the associated strap away from said guide surface and toward said retainer to prevent the associated strap from engaging said discontinuity as the strap traverses said path. 

1. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide surface extending substantially about the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping station, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and means actively applying to the associated strap a force urging it away from said guide surface and toward said retainer only in the region of said path immediately upstream of said discontinuity for preventing the associated strap from engaging said discontinuity as the strap traverses said path.
 2. The binder strap track set forth in claim 1, wherein said path is substantially rectangular in shape.
 3. The binder strap track set forth in claim 1, wherein said strap retainer is movable between a retaining position for cooperation with said strap guide surface to define said path and a releasing accommodating removal of the associated strap from said path.
 4. The binder strap track set forth in claim 1, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperation to form said discontinuity at the junction therebetween.
 5. The binder strap track set forth in claim 1, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junction therebetween, said urging means being carried by said stationary section of said strap guide surface.
 6. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide surface extending substantially about the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping seCtion, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and strap-positioning means for directing a stream of fluid against the associated strap only in the region of said path immediately upstream of said discontinuity to urge the strap away from said guide surface and toward said retainer thereby to prevent the strap from engaging said discontinuity as the strap traverses said path.
 7. The binder strap track set forth in claim 6, wherein said fluid is compressed air.
 8. The binder strap track set forth in claim 6, wherein said strap positioning means directs a plurality of jets of fluid against the associated strap for urging the strap away from said guide surface.
 9. The binder strap track set forth in claim 6, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junctions therebetween.
 10. The binder strap track set forth in claim 6, wherein said strap guide surface includes a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, and said strap retainer includes a stationary section mounted on said stationary section of said strap guide surface and a movable section mounted on said movable section of said strap guide surface for movement therewith, said stationary section and said movable section of said strap guide surface cooperating to form said discontinuity at the junction therebetween, said strap positioning means being carried by said stationary section of said strap guide surface.
 11. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a backing wall having a strap guide surface thereon extending substantially about the strapping station, a strap retainer mounted adjacent to said strap guide surface for cooperation therewith to define a path for the associated strap about the strapping station, the leading end of the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said strap guide surface having a discontinuity therein which impedes the passage of the associated strap therealong, and a fluid conduit formed in said backing wall and adapted to be coupled to an associated source of pressurized fluid, said fluid conduit having an opening therein communicating with the strap path only immediately upstream of said discontinuity and accommodating passage therethrough of a stream of compressed fluid for urging the associated strap away from said guide surface and toward said retainer to prevent the associated strap from engaging said discontinuity as the strap traverses said path.
 12. The binder strap track set forth in claim 11, wherein said path is substantially rectangular in shape, said discontinuity being disposed adjacent to one of the corners of said path.
 13. The binder strap track set forth in claim 11, wherein said conduit has a plurality of openings therein adjacent to said discontinuity communicating with said path and accommodating passage therethrough of a plurality of streams of compressed fluid.
 14. The binder strap track set forth in claim 11, wherein said strap guide surface being substantially planar and having an elongated slot therein adjacent to said discontinuity, said fluid conduit being Received in said slot with a portion of the wall of said conduit having the outer surface thereof disposed substantially coplanar with the adjacent portion of said strap guide surface, said opening being formed in said outer surface of said fluid conduit.
 15. A binder strap track for guiding a binder strap around an object to be bound located at a strapping station, said track comprising a strap guide defining a path for the associated strap extending substantially about the strapping station said strap guide including a stationary section and a movable section coupled to said stationary section and movable with respect thereto for varying the length of said strap guide, each of said sections including a backing wall having a strap guide surface thereon and a strap retainer cooperating with said strap guide surface to define the adjacent section of said path therebetween, the associated strap being normally biased toward engagement with said strap guide surface as the strap traverses said path, said stationary section strap guide surface and said movable section strap guide surface cooperating to form a discontinuity therebetween which impedes the passage of the associated strap therealong, said stationary section backing wall having an elongated slot in said strap guide surface thereof substantially rectangular in transverse cross-section, and a fluid conduit substantially rectangular in cross-section disposed in said slot and adapted to be coupled to an associated source of pressurized fluid, said fluid conduit having an outer wall provided with a plurality of openings therethrough and having the outer surface thereof disposed substantially coplanar with the adjacent portion of the stationary section strap guide surface, said openings accommodating passage therethrough of streams of compressed fluid for urging the associated strap away from said guide surface and toward said retainer to prevent the associated strap from engaging said discontinuity as the strap traverses said path. 